An intriguing and engaging film

Rating: 8/10 (12 May 2007)

I haven't read all the posted comments yet (I browsed through several late last night after seeing this visually stunning and atmospheric film on TV).
A few posts mentioned a "happy ending." The version broadcast here in Melbourne last night did have a happy ending (the three survivors have escaped to the Lakes District and are apparently about to be 'saved' when their large fabric HELLO sign is seen by the jet fighter pilots), then we had all the credits.
This was followed by a black screen with the words "...what if" in the lower right corner, followed by another sequence (a coda) in a hospital operating room, showing Selena's unsuccessful attempts to save Jim, after which she and Hannah leave and walk away into the distance along the hospital corridor - The (real) End.
While this sequence cast a suitably bleak pall over the entire movie (bleakness was one of its strong points), and was a more fitting conclusion than the earlier, clichéd "happy ending" it also made sense of a very short out-of-context sequence seen earlier (Selena filling a hypodermic needle).
There was an interesting scene earlier in the film (when Jim, Selena and Hannah and her father are trying to sleep outdoors) where we're led to believe that what we're seeing is actually happening, only to find that it's Jim's dream.
The whole of the pre-credits sequence (the 'happy' ending, including the deux ex machina of the jet plane) was also Jim's dream, but this time as he was dying, despite Selena's efforts, from his gunshot wound.